SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3fc521ec454e3edc43b50419c8cb50013918ec6175e19393deaabf6178691601' 
  AND token = 'b8+4pnCux9EkSI0c2OO4oXrU1Hc4yEMp7EBzveLTiUU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}